Internal combustions engines convert chemical energy from a fuel into mechanical energy. The fuel may be petroleum-based (gasoline or diesel), natural gas, a combination thereof, or the like. Some internal combustion engines, such as gasoline engines, inject an air-fuel mixture into one or more cylinders for ignition by a spark from a spark plug or the like. Other internal combustion engines, such as diesel engines, compress air in the cylinder and then inject fuel into the cylinder for the compressed air to ignite. A diesel engine may use a hydraulically activated electronically controlled unit injection (HEUI) system or the like to control the fuel injection into the cylinders. The ignited fuel generates rapidly expanding gases that actuate a piston in the cylinder. Each piston usually is connected to a crankshaft or similar device for converting the reciprocating motion of the piston into rotational motion. The rotational motion from the crankshaft may be used to propel a vehicle, operate a pump or an electrical generator, or perform other work. The vehicle may be a truck, an automobile, a boat, or the like.
Each cylinder in an internal combustion engine usually has one or more intake valves and one or more exhaust valves. The intake valves open for air or an air-fuel mixture to enter the cylinder. The exhaust valves open for exhaust cases to exit the cylinder. The internal combustion engine typically uses a camshaft to operate the intake and exhaust valves.
A camshaft typically is a rod with one or more cams that convert the rotational motion of the rod into reciprocating motion. A cam is an irregularly shaped disk or projection extending radially from the rod. When the camshaft rotates, a cam causes a part in contact with the cam to move up and down. In some internal combustion engines, the cams on the camshaft are connected to push rods that actuate rocker arms to operate the intake and exhaust valves. In other internal combustion engines, the cams on the camshaft are connected directly to the intake and exhaust valves for operation. Some internal combustion engines use a single overhead camshaft to operate the intake and exhaust valves. Other internal combustion engines use a double overhead camshaft to operate the intake and exhaust valves.
A double overhead camshaft typically has two camshafts—a first camshaft to operate the intake valves and a second camshaft to operate the exhaust valves. The camshafts are positioned in the cylinder head above the valves. The cams on the camshafts connect directly to the respective intake and exhaust valves. The first camshaft usually has a camshaft gear that is connected by a timing belt or chain to the crankshaft of the internal combustion engine. A cam-to-cam gear connects the camshafts. The cam-to-cam gear usually is mounted on the first camshaft adjacent to the camshaft gear. When the crankshaft rotates, the timing chain causes the camshaft gear to rotate the first camshaft. The rotation of the first camshaft causes the cam-to-cam gear to rotate the second camshaft. The rotation of the camshafts causes the intake and exhaust valves to open and close.
Most internal combustion engines have a fuel pump to supply fuel to the cylinders. Many fuel pumps are mechanically driven by the rotational motion of the engine. Mechanically-driven fuel pumps typically have either a fuel pump gear or a fuel pump pulley to operate the pump.
Some fuel pumps with a fuel pump gear may be connected to a crankshaft gear. An idler gear may be positioned between the fuel pump gear and the crankshaft gear. The idler gear is an additional part that may increase assembly and maintenance costs and may increase power transmission losses from the crankshaft. The connection of the fuel pump gear to the crankshaft gear via an idler gear typically restricts the location of the fuel pump to positions near the crankshaft gear.
Other fuel pumps with a fuel pump gear may be connected to a camshaft gear. The position of the cam-to-cam gear in a double overhead camshaft may prevent or restrict the connection of the fuel pump gear to the camshaft gear. An idler gear and/or other extension to the fuel pump gear may be used, but may increase costs and increase power transmission losses in the engine.
Most fuel pumps with a fuel pump pulley are connected to the crankshaft gear by a drive belt. The drive belt is an additional part that may increase assembly and maintenance costs and may increase power transmission losses from the crankshaft. The drive belt connection of a fuel pump pulley to the crankshaft may increase the space requirements of the engine.